Maintaining a solar power module

ABSTRACT

A solar power system includes a plurality of solar power cells mounted on an outer surface of a spherical frame, the spherical frame including an inner surface that defines an interior volume; a heat sink that includes a hollow housing mounted within the interior volume of the spherical frame; and a phase change material positioned in the hollow housing of the heat sink, the phase change material thermally coupled to the inner surface of the spherical frame to receive heat from the outer surface of the spherical frame.

TECHNICAL FIELD

This document relates to systems and methods for maintaining a solarpower module and, more particularly, cleaning and cooling surfaces of asolar power module.

BACKGROUND

Solar power systems and modules, such as photovoltaic (PV) systems andheliostat systems, operate most efficiently in climates and ambientenvironments that experience a large number of sunny, daytime hours. Insuch climates and ambient environments, however, the large number ofsunny hours can produce conditions that are not optimal for solar powersystem operation. For example, many locations around the Earth thatexperience sunny climates also experience high daytime temperaturescoincident with the sunny hours. Further, many sunny climates are inlocations in which sand, dust, and other particles are prevalent in theambient atmosphere. Climate conditions such as high temperature andatmospheric particles can add challenges to efficient operation of solarpower systems, such as PV cells used in solar panel arrays. For example,while sunny weather increases power output from the solar power arrays,dust and high temperature reduce the efficiency leading to lower solarpower output.

SUMMARY

In a general implementation, a solar power system includes a pluralityof solar power cells mounted on an outer surface of a spherical frame,the spherical frame including an inner surface that defines an interiorvolume; a heat sink that includes a hollow housing mounted within theinterior volume of the spherical frame; and a phase change materialpositioned in the hollow housing of the heat sink, the phase changematerial thermally coupled to the inner surface of the spherical frameto receive heat from the outer surface of the spherical frame.

In an aspect combinable with the general implementation, the pluralityof solar power cells include a plurality of photovoltaic (PV) cells.

In another aspect combinable with any of the previous aspects, the phasechange material includes at least one paraffin wax.

Another aspect combinable with any of the previous aspects furtherincludes at least one permanent magnet mounted within the interiorvolume.

In another aspect combinable with any of the previous aspects, the atleast one permanent magnet is mounted within the interior volume on ashaft that extends through a diameter of the spherical frame and theheat sink.

In another aspect combinable with any of the previous aspects, the atleast one permanent magnet includes a hollow magnet that encloses theheat sink.

Another aspect combinable with any of the previous aspects furtherincludes a magnetized heat transfer fluid disposed and flowable withinthe interior volume of the spherical frame between the hollow magnet andthe inner surface of the spherical frame based, at least in part, on anamount of heat transferred from the outer surface of the spherical frameinto the magnetized heat transfer fluid and a magnetic field generatedby the hollow magnet.

Another aspect combinable with any of the previous aspects furtherincludes a plurality of baffles mounted within the interior volume ofthe spherical frame between the heat sink and the inner surface of thespherical frame.

In another aspect combinable with any of the previous aspects, theplurality of baffles form at least one flowpath for the magnetized heattransfer fluid within the interior volume that is oriented along acircumference of the interior surface of the spherical frame.

Another aspect combinable with any of the previous aspects furtherincludes at least one permanent ring magnet circumferentially mountedadjacent an outer surface of the spherical frame.

Another aspect combinable with any of the previous aspects furtherincludes a magnetized heat transfer fluid disposed and flowable withinthe interior volume of the spherical frame between the heat sink and theinner surface of the spherical frame based, at least in part, on anamount of heat transferred from the outer surface of the spherical frameinto the magnetized heat transfer fluid and a magnetic field generatedby the permanent ring magnet.

In another general implementation, a method for cooling a solar powersystem includes operating a solar power system that includes a pluralityof solar power cells mounted on a spherical frame; transferring heatfrom an outer surface of the spherical frame to an inner surface of thespherical frame and to a heat sink mounted within an interior volume ofthe spherical frame; transferring the heat from the heat sink to a phasechange material positioned in the heat sink; and transforming at least aportion of the phase change material from a solid phase to a semi-solidor liquid phase based on the heat received from the outer surface of thespherical frame.

In an aspect combinable with the general implementation, the pluralityof solar power cells include a plurality of photovoltaic (PV) cells.

In another aspect combinable with any of the previous aspects, the phasechange material includes at least one paraffin wax.

Another aspect combinable with any of the previous aspects furtherincludes generating a magnetic field within the interior volume of thespherical frame with at least one magnet; transferring heat from anouter surface of the spherical frame to a magnetized fluid containedwithin the interior volume; and circulating the magnetized fluid withinthe interior volume between the inner surface of the spherical frame andthe heat sink based on the generated magnetic field and an amount ofheat transferred from the outer surface to the magnetized fluid.

In another aspect combinable with any of the previous aspects, themagnetized heat transfer fluid includes a ferrofluid liquid thatincludes a plurality of magnetized particles.

In another aspect combinable with any of the previous aspects, the atleast one magnet includes a permanent magnet.

In another aspect combinable with any of the previous aspects,generating the magnetic field includes generating the magnetic fieldfrom the at least one magnet mounted within the interior volume on ashaft that extends through a diameter of the spherical frame.

In another aspect combinable with any of the previous aspects, the atleast one magnet includes a spherical magnet that encloses the heatsink.

In another aspect combinable with any of the previous aspects,generating the magnetic field includes generating the magnetic fieldwith a plurality of ring magnets mounted adjacent the spherical frame.

In another aspect combinable with any of the previous aspects,circulating the magnetized fluid within the interior volume includescirculating the magnetized fluid through a flowpath within the interiorvolume formed by a plurality of baffles mounted within the interiorvolume of the spherical frame.

Another aspect combinable with any of the previous aspects furtherincludes rotating, based at least partially on circulation of themagnetized fluid within the interior volume, the spherical frame aboutan axis of rotation.

One, some, or all of the implementations according to the presentdisclosure may include one or more of the following features. Forexample, a solar power system according to the present disclosure mayincrease efficiency (for example, electrical power output) of aphotovoltaic power system. A solar power system according to the presentdisclosure may facilitate in-situ cleaning of PV cells with little to nodisassembly of the solar power system. As another example, multipleself-cleaning arrays of solar power systems can be linked easily inareas such as sun shades and car parks. Also, a solar power systemaccording to the present disclosure may include a spherical design thatprovides 150% more surface area for the exposed hemispherical region forsolar absorption than a planar solar panel. As another example, a solarpanel cleaning system of a solar power system may also act as a heattransfer mechanism to reduce a surface temperature of a solar panel ofthe system. As another example, the cleaning system of a solar powersystem of the present disclosure may experience little to no evaporationof a cleaning solution, as well as little to no friction between thesolar panel and the cleaning system, through a ferrofluid seal.

One, some, or all of the implementations according to the presentdisclosure may also include one or more of the following features. Forexample, a solar power system according to the present disclosure mayalso use a low or no energy magneto-caloric pump mechanism to circulatea cooling fluid to cool a solar panel of the power system. A solar powersystem according to the present disclosure may utilize permanent magnetsto drive the magneto-caloric pump, which in turn may rotate a sphericalsolar panel of the system. A solar power system according to the presentdisclosure may also utilize a heat transfer material which requires nopower to cool the solar panel of the power system. As another example,the solar power system may include cooling and cleaning systems that uselittle to no power and require little to no maintenance.

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic illustration of at least a portion of a solarpower system.

FIG. 1B is a schematic illustration of at least a portion of a solarpower system that includes a solar panel cleaning assembly.

FIG. 2 is a schematic illustration of an internal sectional view of atleast a portion of a solar power system that includes at least onemagnet and a magnetized fluid to cool the solar power system.

FIG. 3 is a schematic illustration of at least a portion of anothersolar power system that includes at least one magnet and a magnetizedfluid to cool the solar power system, along with a solar panel cleaningassembly.

FIG. 4 is a schematic illustration of an example operation of a magneticfluid pump.

FIG. 5 is a schematic illustration of at least a portion of a solarpower system that includes at least one magnet and a solar panelmounting assembly.

FIG. 6 is a schematic illustration of at least a portion of a solarpower system that includes an inner spherical housing.

FIG. 7 is a schematic illustration of at least a portion of a solarpower system that includes at least one magnet mounted in an innerspherical housing and a magnetized fluid to cool the solar power system,along with a phase change heat transfer material.

FIG. 8A is a schematic illustration of at least a portion of a solarpower system that includes at least one toroidal magnet and a magnetizedfluid to cool the solar power system.

FIG. 8B is a schematic illustration of a magnetic fluid seal system thatmay be implemented with a solar power system that includes a solar panelcleaning assembly.

FIGS. 9A-9B are schematic illustrations of at least a portion of anothersolar power system that includes at least one ring magnet and amagnetized fluid to cool the solar power system, along with a solarpanel cleaning assembly.

FIG. 10 is a chart that illustrates solar panel module efficiency as afunction of module temperature.

DETAILED DESCRIPTION

FIG. 1A is a schematic illustration of at least a portion of a solarpower system 100. FIG. 1A shows the solar power system 100 from a sideview, where the solar power system 100 includes a solar panel 105. Inthis example embodiment, the solar panel 105 is spherically-shaped andmounted on mounting assemblies 115 along an axis (for example, an axisof rotation) 210. In alternative implementations, the solar panel 105may be, for example, cylindrically-shaped, cubically-shaped, or otherform that may be rotated about an axis. Other example shapes of thesolar panel 105 include, for instance, cylinders with hemisphericalends, as well as cylinders with solar power cells (for example,photovoltaic cells) mounted on gears or spines that extend from alateral surface of the cylinder. As another example, solar power cellsmay be mounted to fins or spines that extend from a shaft (rather than acylinder).

As shown in this example, the axis 215 extends through a diameter of thesolar panel 105. Generally, the mounting assemblies 115 (for example,brackets, rotatable armatures, piston/cylinder assemblies, or otherwise)may facilitate installation of the solar power system 100 to a supportstructure (not shown), such as a roof, a terranean surface, a buildingstructure, or other support structure. The solar power system 100 may beone of multiple solar power system 100 arranged in an array to generateelectrical power from solar energy. Turning briefly to FIG. 5, thisfigure shows a schematic illustration of at least a portion of the solarpower system 100 that includes at least one magnet 185 (described later)and a more detailed view of the solar panel mounting assembly 115. Asshown in FIG. 5, the solar panel mounting assembly 115 includes abracket 121 from which a shaft or coupling 240 extends into a bearing235. The bearing 235, as shown receives the coupling 240 and a shaft 175that extends through the spherical frame 120 at the axis 215. In someaspects, the shaft 175 and coupling 240 may be integral such that thecoupling 240 is part of the shaft 175. A spacer 230 (for example, thatcomprises bearing surfaces) is mounted to the shaft 175 between theouter surface 125 of the spherical frame 120 and the bearing 235. Asshown, the solar panel mounting assembly 115 may provide for reducedfriction rotation of the spherical frame 120 attached to the shaft 175,when the shaft 175 is actuated to turn.

Generally, the solar power system 100 receives solar energy from the Sunthrough multiple photovoltaic (PV) cells 110, and converts the receivedsolar energy to direct current (DC) electricity. The solar energyconsists of light energy (i.e., photons), from the Sun that can betransformed to electricity through the photovoltaic effect. Generally,each PV cell 110 absorbs the photons, which excites an electron residingon a semiconductor material to a higher-energy state. The excitedelectron (or electrons, as this process occurs for millions of electronsduring operation of the PV cell 110) produces a voltage, which in turncan produce a DC through conduits (not shown) that are electricallycoupled to the solar panel 105 (to the PV cells 110 in series). The DCcarried in the conduits are delivered, typically, to an inverter systemto convert the DC to alternating current (AC). Such electricalconnections are made with the PV cells 110 in series to achieve anoutput voltage and a parallel desired current.

As shown in FIG. 1A, the solar panel 105 includes a spherical frame 120with an outer surface 120 to which the PV cells 110 are mounted. In thisexample implementation, the spherical frame 120 may be solid or may behollow. The spherical frame 120 is coupled to the mounting assemblies115 to support the solar panel 105 and, in some aspects, allowrotational movement of the solar panel 105 about the axis 210.

FIG. 1B is a schematic illustration of at least a portion of the solarpower system 100 that includes a solar panel cleaning assembly. In thisimplementation, the solar panel cleaning system of the solar powersystem 100 includes, as shown, a reservoir 130 that surrounds a lowerhemisphere 220 of the solar panel 105 and a cleaning solution 135 thatis enclosed at least partially within the reservoir 130. Generally, thesolar panel cleaning system in this example implementation may providefor automated cleaning of the solar panel 105, for example, to removecollected dust and other particles from the PV cells 110 by rotating thespherical frame 120 on the axis of rotation 210 to immerse an upperhemisphere 215 of the solar panel 105 within the cleaning solution 135(for example, a cleaning liquid).

For example, in some aspects, deposits of dust and other particles onthe surface of the PV cells 105 may block or partially block solarradiation from reaching the cells 110 (for example, through a glasscover on the cells 110). A density of deposited dust, as well asparticle composition and particle distribution, can have an impact onthe power output and current voltage and characteristics of the solarpower system 100. For example, in certain Middle Eastern environments(for example, Dhahran, Saudi Arabia) the effect of dust accumulation onthe power output of the PV cells 110 (for example, as mono-crystallinePV cells or polycrystalline PV cells) can gradually decrease poweroutput if no cleaning is performed to remove the dust. In some cases,such deleterious effects can reduce power output by more than 50% withno cleaning. In some cases, even a single dust storm that depositsparticles at on the PV cells 110 may decrease the power output by 20%.

The cleaning solution 135 may include or more chemicals formulated toremove particles from the PV cells 110, prevent or help preventmineralization buildup on the PV cells 110, or both. For example, insome aspects, commercial products such as Solar Panel Wash from AmericanPolywater® Corp., NuRinse (several products) from NuGenTec®, Aquaeasefrom Hubbard-Hall, or Solar Clean, Powerboost and Titan Glass GleamSolar from J.Racenstein®. In some aspects, the cleaning solution 135 maybe a water-based solution mixed with ethoxylated alcohols. In someaspects, the cleaning solution 135 may be a diluted soap-water mixture.

As further shown in FIG. 1B, an actuator 117 may be mounted to one ormore of the mounting assemblies 115 to provide rotation of the sphericalframe 120 so as to rotate the upper hemisphere 215 through the cleaningsolution 135. For example, the actuator 117 may be coupled to a shaft(shown in other figures) that extends through or from the mountingassembly 115 and to or through the spherical frame 120. In some aspects,the actuator 117 may include or be a manual actuator, such as a handleor lever, thus allowing a human operator to rotate the spherical frame120. In some aspects, the actuator 117 may include or be a motorized orautomatic actuator, such as a hydraulic, electric, or solar poweredmotor, that can automatically (for example, upon receipt of a commandfrom a control system, at a predetermined time, within prearranged timeperiods, or based on a density of particles on the PV cells 110) rotatethe spherical frame 120.

Upon rotation (for example, by a manual or motorized actuator), the PVcells 110 mounted on the upper hemisphere 215 of the solar panel 105 maybe immersed in the cleaning solution 135 within the reservoir 130. Insome aspects, PV cells 110 may be mounted only on the upper hemisphere215. Thus, in such aspects, the upper hemisphere 215 with the PV cells110 may be rotated into the reservoir 130 to reside in the cleaningsolution 135 for a particular time duration. As no PV cells may bemounted on the lower hemisphere 220, the solar power system 100 may notbe operational (for example, produce DC) during this cleaning operation.Subsequently, the upper hemisphere 215 may be rotated out of thereservoir 130 to resume operation (for example, producing DC).

In some aspects, PV cells 110 may be mounted on the upper hemisphere 215and the lower hemisphere 220 (for example, on the whole outer surface125 of the spherical frame 120). Thus, in such aspects, the upperhemisphere 215 with the PV cells 110 may be rotated into the reservoir130 to reside in the cleaning solution 135 to be cleaned, while the PVcells 110 mounted to the lower hemisphere 220 operate to produce DC. Thesolar power system 100 may remain in such a position for a time durationthat may be longer than the particular time duration in the case of PVcells 110 only being mounted to the upper hemisphere 215. Subsequent tothat longer duration, or when the PV cells 110 mounted on the lowerhemisphere 220 are in need of cleaning, the upper hemisphere 215 may berotated out of the reservoir 130 to continue of the solar power system100 with little to no interruption of operation (for example, producingDC).

In some aspects, the cleaning solution 135 within the reservoir 130 mayalso provide a cooling fluid for the solar power system 100. Forexample, the PV cells 110 mounted to whichever hemisphere (for example,upper 215 or lower 220) of the solar panel 105 that is immersed in thereservoir 130 may be cooled to or sustained at a particular desiredtemperature that is a temperature (or close to a temperature) of thecleaning solution 135.

As shown, the solar panel cleaning system of the solar power system 100may also include a seal 140 mounted to the top of the reservoir 130. Theseal 140 may be a cover for the reservoir 130, for example, to preventloss (for example, due to evaporation, spillage, or otherwise) of thecleaning solution 135 from the reservoir 130. The seal 140, in someaspects, may also contact the PV cells 110 to prevent leakage of thecleaning solution 135 from the reservoir 130 (for example, due totipping of the solar power system 100). Other seals, such as magneticfluid seals, are also contemplated by the present disclosure and areexplained with reference to FIGS. 8A-8B.

The example embodiment of the solar power system 100 shown in FIG. 1Balso includes a fill conduit 145 and a drain 145 that are fluidlycoupled to the reservoir 130. For example, a volume of the cleaningsolution 135 may be replenished from a cleaning solution source 160 (forexample, tank, bottle, or other liquid holding device) through the fillconduit 145. In some cases, for example, the cleaning solution source160 may also include, for example, a float valve and a pump that operateto circulate cleaning solution 135 to the reservoir 130 through the fillconduit 145 when the float valve determines that a volume of thesolution 135 in the reservoir 130 is below a predetermined or desiredminimum volume.

The drain 150 may be fluidly coupled to the reservoir 130 to a solutionrecapture system 165. In some aspects, because the used cleaningsolution 135 within the reservoir 130 may contain dissolved particles,dust, or other contaminants, a filter 155 may be provided in the drain150. The drain 150 may be opened (for example, by a valve or otherorifice control device) manually or automatically to circulate usedcleaning solution 135 from the reservoir 130 to the solution recapturesystem 165. Subsequently, the solution recapture system 165 may recycle(for example, further clean) the used cleaning solution 135 and supplythe recycled solution to the cleaning solution source 160, or mayinclude a tank or other enclosure to store used cleaning solution thatis to be disposed.

In an example operation of the solar power system 100 shown in FIG. 1B,the solar panel 105 may operate to generate electricity in a normaloperation mode. At a particular time, a determination may be made toclean the portion of PV cells 110 that are exposed to an ambientenvironment (for example, the cells 110 on the upper hemisphere 215),such as at a particular predetermined time interval, upon visualinspection of the exposed PV cells 110, or when a determined density ofparticles on the exposed PV cells 110 exceeds a threshold value. Theactuator 117 may be operated (for example, manually or automatically) torotate the spherical frame 120 about the axis 210. Upon rotation, theexposed PV cells 210 may be immersed into the cleaning solution 135 thatis contained in the reservoir 130. The immersed PV cells 110 may remainin the solution 135 for a particular time duration (for example,determined based on an amount of time necessary to remove particles fromthe cells 110).

In some aspects, during cleaning of a portion of the PV cells 110mounted on the solar panel 105, another portion of PV cells 110 (forexample, mounted on the lower hemisphere 220) may continue electricityproduction for the solar power system 100, as rotation of the sphericalframe 120 exposes the other portion of the PV cells 110 to the ambientenvironment. After the particular time duration expires, the actuator117 may rotate the spherical frame 120 to move the cleaned (and cooled)PV cells 110 into exposure to the ambient environment. Intermittently orperiodically, the cleaning solution 135 in the reservoir 130 may bereplenished by circulating new solution 135 from the cleaning solutionsource 160, through the fill conduit 145, and into the reservoir 130.Also, intermittently or periodically, used cleaning solution 135 thatcontains, for example, dissolved particulates, may be circulated fromthe reservoir 130 and through the filter 155 to the drain 150. Thefiltered solution 135 may be circulated to the solution recapture system165 for recycling or disposal.

FIG. 2 is a schematic illustration of an internal sectional view of atleast a portion of the solar power system 100 that includes at least onemagnet 185 and a magnetized fluid 180 to cool the solar power system100. FIG. 2, as shown, illustrates a side-sectional view of the solarpower system 100 taken through a diameter of the spherical frame 120.Generally, FIG. 2 shows an example embodiment of a solar power systemcooling system that uses magnet 185 to circulate magnetized fluid 180through an interior volume 190 of the spherical frame 120. Bycirculating the magnetized fluid 180 within the interior volume 190,heat from the PV cells 110 (not shown in this figure) may be transferredthrough the spherical frame 120 (for example, from the outer surface 125to an inner surface 170) and into the magnetized fluid 180. Heatreceived into the magnetized fluid 180 may be transferred, for example,to a heat sink (described later), the cleaning solution 135, or othercooling source (for example, a cooling coil, Peltier cooler, or othercooling source in thermal communication with the magnetized fluid 180).

In some aspects, overheating (or heating) of solar power systems, suchas the solar power system 100, may have deleterious effects on theoperation of the system in producing electricity. For example, PV cellperformance may decrease with increasing temperature, as operatingtemperature may affect the photovoltaic conversion process. Both theelectrical efficiency and the power output of a PV cell decrease withincreasing cell temperature. In desert applications, for instance, PVcells are often sensitive to overheating. For example, PV cells in theMiddle East (for example, Dhahran, Saudi Arabia) may experience a lossof efficiency as operating temperature increases, as shown in chart 1000in FIG. 10.

As shown in chart 1000 of FIG. 10, PV cell efficiency can decrease from11.6% to 10.4% when module temperature increases from 38° C. to 48° C.,which corresponds to 10.3% losses n efficiency and a temperaturecoefficient of −0.11 ΔE/%° C. PV cell operating temperatures over 26° F.can begin reducing output efficiency, and as the temperature of a solarpanel increases, the output current increases exponentially while thevoltage output is reduced linearly. The cooling system illustrated inFIG. 2 can counter the efficiency loss of PV cells 110 in hightemperature environments.

As shown, the magnetized fluid 180 is contained within the sphericalframe 120 and free to circulate within the interior volume 190.Circulation of the magnetized fluid 180 may be at least partiallygenerated by the magnet 185 mounted on shaft 175 that extends throughthe diameter of the spherical frame 120. In this example implementation,the magnet 185 is a spherically-shaped permanent magnet and generates amagnetic field 225 within the interior volume 190 of the spherical frame120.

In some aspects, the magnetic fluid 180 is a ferrofluid (for example,liquid). Ferrofluids consist of a carrier fluid loaded with small (forexample, nanometer sized) magnetic particles. The behavior offerrofluids varies due to, for example, the carrier fluid, temperature,particle size, shape and loading, magnetic characteristics of theparticles and the applied magnetic field (for example, magnetic field225). When exposed to the magnetic field 225, the magnetized particlesin the magnetized fluid 180 produce a body force. In addition,ferrofluid particle size ensures that thermal agitation in the fluidkeeps the particles in suspension. Ferrofluids may be expected toperform at temperature of 150° C. (for example, continuously) or 200° C.(for example, intermittently).

As shown in FIG. 2, circulation curves represent the circulatorymovement of the magnetized fluid 180 that is due, at least in part, tothe magnetic field 225 (directed to cause the illustrated rotation)generated by the spherical magnet 185. As heat is being transferred tothe magnetized fluid 180 during circulation (for example, heat from thePV cells 110), the system acts as a ferrofluid, or magneto-caloric,pump. For example, with reference briefly to FIG. 4, a magneto-caloricpump is a device which moves magnetic substances (the magnetized fluid180) from a region of low pressure to a region of high pressure createdby a heat source (the PV cells 110 that transfer heat into the interiorvolume 190 of the spherical frame 120).

FIG. 4 shows a generic schematic illustration of the operation of amagneto-caloric pump applied to the solar power system 100, whichrepresents an example operation of the described cooling system of thesolar power system 100 shown in FIG. 2. The “pump,” in this case, refersto a flowpath of forced circulation due to the magnetic field 225 and apressure differential caused by heating of the magnetized fluid 180within the interior volume 190. The pump contains a magnetic field(field 225) and a heat source (heat from the PV cells 110). Under theinfluence of the magnetic field 225, magnetized fluid 180 is drawn intothe pump. As it proceeds along the pump, the fluid 180 is heated by theheat source until the temperature of the magnetized fluid 180 reaches apoint where there is a significant reduction in the ferromagneticproperties of the material (for example, the nanoparticles in thefluid). Generally, this happens when the material temperature approachesthe “Curie Point” (for example, the temperature at which a materialloses its permanent magnetic properties, to be replaced by inducedmagnetism).

The low temperature incoming magnetized fluid (for example, magnetizedfluid 180 that flows through the lower hemisphere 220) is attracted bythe magnetic field contained in the pump. The heated material (forexample, heated magnetized fluid 180 flowing in the upper hemisphere215) in the pump is no longer influenced by the magnetic field and isexpelled from the pump by the incoming material (for example, coolermagnetized fluid 180 flowing upward from the lower hemisphere 220 to theupper hemisphere 215). A pressure head is created in the pump. The hotmaterial (for example, magnetized fluid 180 from the upper hemisphere215) from the pump is dissipated and returned to the pump input (forexample, volume of the spherical frame 120 within the lower hemisphere220), completing the pumping cycle.

FIG. 3 is a schematic illustration of at least a portion of anotherembodiment of the solar power system 100 that includes at least onemagnet 205 to circulate a magnetized fluid to cool the solar powersystem 100. FIG. 3 also shows the components of the solar panel cleaningassembly described previously with reference to FIG. 1B. FIG. 3 shows aside-view of this example of the solar power system 100. In this exampleembodiment, in addition to, or alternatively to, a spherical permanentmagnet 185 mounted within the interior volume 190 of the spherical frame120 (not shown in this figure, but shown in FIG. 2), one or morepermanent ring magnets 205 may be mounted circumferentially adjacent theouter surface 125 of the spherical frame 120.

As shown, the permanent ring magnets 205 may be mounted to a cage ring195 that is a circular structure that circumferentially surrounds thespherical frame 120. The permanent ring magnets 205 can also be mounted,as shown, to one or more cages 200 that are also mounted to the cagering 195 circumferentially around the spherical frame 120. Asillustrated, the cages 200 are mounted such that a diameter of each cage200 is orthogonal to a diameter of the cage ring 195.

The operation of the embodiment of the solar power system 100 shown inFIG. 3 is similar to the operation of the solar power system 100 shownin FIG. 2, with the difference being that the magnetic field within theinterior volume 190 of the spherical frame 120 is generated by thepermanent ring magnets 205 rather than, or in addition to, a permanentmagnet mounted within the interior volume 190 (for example, magnet 185).Thus, the permanent ring magnets 205 may generate the magnetic fieldthat at least partially powers the magneto-caloric pump applied to thesolar power system 100 as described previously.

As further shown in FIGS. 2 and 3, the spherical frame 120 may also berotated (shown by rotations 187) by operation of the magneto-caloricpump described above. For example, ferrofluid migration (for example,movement of the magnetized fluid 180 within the volume 190) from cool towarm portions of the volume 190 may create a pressure differentialsufficient to rotate the spherical frame 120 on the shaft 175. In someaspects, as shown and discussed later with reference to FIGS. 9A-9B, therotation can be realized or enhanced through a balanced spherical frame120 (for example, on the shaft 175) and the flow of the magnetized fluid180 through flow channels formed by baffles mounted on the inner surface170 of the spherical frame 120.

For instance, as the magnetized fluid 180 circulates within the interiorvolume 190 as shown, a rotational force may be exerted on the interiorsurface 170 of the spherical frame 120 by the moving fluid 180. Thisrotational force may cause the spherical frame 120 (if free to rotate onthe shaft 175) to rotate as well about the axis 210. In some aspects,such rotation of the frame 120 may be desirable, for example, forautomatic cleaning of the PV cells 110 by periodically rotating thesolar panel 105 through the cleaning solution 135 (shown in FIGS. 1B and3). In some aspects, the rotational speed of the spherical frame 120 maybe based at least partially on a temperature gradient between the heatedmaterial (for example, magnetized fluid 180 within the upper hemisphere215) and the cooled material (for example, magnetized fluid 180 withinthe lower hemisphere 220).

FIG. 6 is a schematic illustration of at least a portion of the solarpower system 100 that includes an inner spherical housing 245. FIG. 2,as shown, illustrates a side-sectional view of the solar power system100 taken through a diameter of the spherical frame 120 and the innerspherical housing 245. The inner spherical housing 245 is mounted on theshaft 175 and defines an additional interior volume of the interiorvolume 190 of the spherical frame 120. An annulus 191 is further definedbetween the inner surface 170 of the spherical frame 120 and the innerspherical housing 245.

Generally, the inner spherical housing 245 provides an enclosure for, assome examples, one or more permanent magnets (such as magnet 185)mounted on the shaft 175, a heat sink (as described later), or toenclose other components of the solar power system 100. For example,FIG. 7 is a schematic illustration of at least a portion of the solarpower system 100 that includes at least one magnet 250 mounted in theinner spherical housing 245, along with a heat transfer material 260that is disposed within a volume encompassed by the magnet 250. In thisimplementation, the inner spherical housing 245 is separate from thespherical (permanent) magnet 250, which is mounted within the volume ofthe housing 245. In alternative implementations, the spherical magnet250 may form a housing that defines the volume into which the heattransfer material 260 is disposed.

The spherical magnet 250 may be mounted on the shaft 175 and generates amagnetic field (not shown here) much like the magnetic field 225 isgenerated by spherical magnet 185 in FIG. 2. Thus, the spherical magnet250 may generate a magnetic field within the interior volume 190 of thespherical frame 120 that at least partially powers the magneto-caloricpump applied to the solar power system 100 as described previously. Inthis example, therefore, the spherical magnet 250 generates the magneticfield that drives (along with a temperature gradient) the magnetizedfluid 180 within the interior volume 190 and in the annulus 191.

The inner volume of the inner spherical housing 245 may include ordefine a heat sink (for example, in embodiments with or without thespherical magnet 250). The hint sink includes the heat transfer material260. For example, the heat sink within the housing 245 may provide for acentral volume available for absorbance of thermal energy, for example,from the PV cells 110. This central volume can be used in the form ofvarious heat exchange technologies including chemical absorption throughthe melting of calcium hydroxide (Ca(OH)₂) crystals in a aqueoussolution or through the use of a tunable phase change material (PCM).Either material, as well as other examples, can be used as the heattransfer material 260. Further, an amount of material may be adjusted(and adjustable) based on the formulation of heat transfer materialincluded within the heat sink and by adjusting the size of the innerspherical housing 245, spherical frame 120, solar panel 105, or acombination thereof, to provide a desired heat transfer amount. Further,in some aspects, the heat transfer material 260 can absorb thermalenergy from the PV cells 110 during a daylight operation time of thesolar power system 100 and phase change from solid to liquid byabsorbing the thermal energy. The heat transfer material 260 can thensolidify during a nighttime non-operational time (for example, when noor negligible solar energy is incident on the solar power system 100) asambient temperature surrounding the solar power system 100 decreases.

In some aspects, the heat transfer material 260 is a PCM such as one ormore paraffin waxes. For example, paraffin wax is typically found as awhite, odorless, tasteless, waxy solid, with a typical melting pointbetween about 46° C. and 68° C. (115° F. and 154° F.). Some paraffinproducts have melting temperatures of 270° F. In some aspects, the heattransfer material 260 may be a blend of paraffin waxes with differentmelting points to more evenly and slowly change phase from solid toliquid as thermal energy is absorbed. For example, a combination andquantity of low, middle, and high temperature compositions may beformulated based on the amount of heat required for removal from the PVcells 110. In some cases, the melting point of a paraffin wax can bedepressed using mixtures of high long chained organic acids and saltsolutions. Table 1 shows example commercial paraffin waxes fromInternational Group Inc. that could be used, individually or incombination, as the heat transfer material 260.

TABLE 1 Astorstat ® Start to Volume of Congealing Open Point ExpansionTravel Point (Astor ® Terminal Point (Astor (Astor Product (ASTM D938)DST-007) (Astor DST-007) DST-007) DST-007) Low Operating TemperatureRange Astorstat HA16 17.8-18.9° C. 17.8-18.9° C. 23.4-24.5° C. 14-18%5.88-6.89 mm 64-66° F. 64-66° F. 74-76° F. 0.23-0.27 in Astorstat HA1827.2-28.3° C. 27.2-28.3° C. 32.8-33.9° C. 14-18% 5.88-6.89 mm 81-83° F.81-83° F. 91-93° F. 0.23-0.27 in Astorstat HA20 36.7-37.8° C. 36.7-37.8°C. 42.3-43.4° C. 16-20% 6.37-7.41 mm 98-100° F. 98-100° F. 108-110° F.0.25-0.29 in Astorstat HA300B 41-42.5° C. 26-28° C. 46-48° C.  9-13%4.85-5.62 mm 106-108.5° F. 78.8-82.5° F. 115-118.5° F. 0.19-0.20 in MidOperating Temperature Range Astorstat 75 80.1-81.2° C. 74.5-75.6° C.85.6-86.7° C. 14-16% 5.88-6.37 mm 176-178° F. 166-168° F. 186-188° F.0.23-0.25 in Astorstat 80 85.1-86.2° C. 79.5-80.5° C. 90.6-91.7° C.14-16% 5.88-6.37 mm 185-187° F. 175-177° F. 195-197° F. 0.23-0.25 inAstorstat 90 95.1-96.2° C. 89.5-90.6° C. 100.6-101.7° C. 14-16%5.88-6.37 mm 203-205° F. 193-195° F. 213-215° F. 0.23-0.25 in Astorstat95 100-101.2° C. 89.0-90.1° C. 105.6-106.8° C. 14-16% 5.88-6.37 mm212-214° F. 192-194° F. 222-224° F. 0.23-0.25 in High OperatingTemperature Range Astorstat 6920 124-129.5° C. 107.3-112.9° C.126.8-132.3° C. 16-18% 6.37-6.89 mm 255-265° F. 225-235° F. 260-270° F.0.25-0.27 in Astorstat 6988 130-135° C. 115.6-121.2° C. 129.5-135.1° C.16-18% 6.37-6.89 mm 265-275° F. 240-250° F. 265-275° F. 0.25-0.27 inAstorstat 10069 105-106° C. 98.4-100.0° C. 114.5-116.2° C. 14-16%5.88-6.37 mm 221-223° F. 209-212° F. 238-241° F. 0.23-0.25 in Astorstat10316 109-110.6° C. 104-105.6° C. 125.7-127.9° C. 15-17% 6.13-6.63 mm228-231° F. 219-222° F. 258-262° F. 0.24-0.26 in

FIG. 8A is a schematic illustration of at least a portion of the solarpower system 100 that includes at least one toroidal magnet 265 and themagnetized fluid 180 to cool the solar power system 100. FIG. 8A, asshown, illustrates a side-sectional view of the solar power system 100taken through a diameter of the spherical frame 120. Generally, FIG. 8Ashows an example embodiment of a solar power system cooling system thatuses the toroidal magnet 265 to generate a magnetic field 270 tocirculate the magnetized fluid 180 through the interior volume 190 ofthe spherical frame 120. By circulating the magnetized fluid 180 withinthe interior volume 190, heat from the PV cells 110 (not shown in thisfigure) may be transferred through the spherical frame 120 (for example,from the outer surface 125 to an inner surface 170) and into themagnetized fluid 180. Heat received into the magnetized fluid 180 may betransferred, for example, to a heat sink (described previously), thecleaning solution 135, or other cooling source (for example, a coolingcoil, Peltier cooler, or other cooling source in thermal communicationwith the magnetized fluid 180). As shown, the magnetized fluid 180 iscontained within the spherical frame 120 and free to circulate withinthe interior volume 190. Circulation of the magnetized fluid 180 may beat least partially generated by the magnet 265 mounted on shaft 175 thatextends through the diameter of the spherical frame 120.

FIG. 8B is a schematic illustration of a magnetic fluid seal system thatmay be implemented with the solar power system 100 that includes a solarpanel cleaning assembly. For example, as illustrated FIG. 8A includesthe solar panel cleaning assembly which includes the reservoir 130hemispherically positioned around the lower hemisphere 220 of thespherical frame 120. The reservoir 130 holds the cleaning solution 130.The magnetic fluid seal system, in this example implementation,comprises a ferrofluid seal that uses a magnetized fluid to create aseal so that a liquid (for example, the cleaning solution 135) does notescape a container (for example, the reservoir 130). As illustrated, themagnetic fluid seal system includes a magnet 275 mounted between thereservoir 130 and the outer surface 125 of the spherical frame 120. Themagnet 275 includes pole pieces 280 and generate a magnetic flux 285.The magnetic flux 285 travels through a ring of magnetic fluid 290 toenergize the particles within the fluid 290. The magnetic fluid 290,which is held against the outer surface 125 of the spherical frame 120and the pole piece 280 by the flux 285, creates a fluidic seal toprevent or help prevent the cleaning solution 135 from escaping thereservoir 130.

FIGS. 9A-9B are schematic illustrations of at least a portion of anotherembodiment of the solar power system 100 that includes at least one ringmagnet 300 the solar panel cleaning assembly. FIG. 9A, as shown,illustrates a side-sectional view of the solar power system 100 takenthrough a diameter of the spherical frame 120. FIG. 9B, as shown,illustrates a top-sectional view of the solar power system 100 takenthrough the ring magnet 300. Generally, FIGS. 9A-9B show an exampleembodiment of a solar power system cooling system that uses the ringmagnet 300 (for example, mounted circumferentially around the sphericalframe 120 at the axis 210) to generate a magnetic field to circulate amagnetized fluid (not shown in this figure) through the interior volume190 of the spherical frame 120. By circulating the magnetized fluidwithin the interior volume 190, heat from the PV cells 110 (not shown inthis figure) may be transferred through the spherical frame 120 (forexample, from the outer surface 125 to an inner surface 170) and intothe magnetized fluid 180. Heat received into the magnetized fluid may betransferred, for example, to a heat sink (described previously), thecleaning solution 135, or other cooling source (for example, a coolingcoil, Peltier cooler, or other cooling source in thermal communicationwith the magnetized fluid 180).

FIGS. 9A-9B also show an example embodiment of the spherical frame 120that includes one or more baffles 305 formed (for example, attached toor integral with) the inner surface 170 of the frame 120. The baffles305 form flow paths 310 through which the magnetized fluid flows duringcirculation of the fluid through the interior volume 190. For example,as previously described, ferrofluid migration (for example, movement ofthe magnetized fluid within the volume 190) from cool to warm portionsof the volume 190 may create a pressure differential sufficient torotate the spherical frame 120 on a shaft (for example, shaft 175, notshown in these figures). In some aspects, the rotation can be realizedor enhanced through a balanced spherical frame 120 (for example, on theshaft) and the flow of the magnetized fluid through flow channels formedby baffles 305 mounted on the inner surface 170 of the spherical frame120. For instance, as the magnetized fluid circulates within theinterior volume 190 as shown, a rotational force may be exerted on theinterior surface 170 of the spherical frame 120 by the moving fluid.This rotational force may cause the spherical frame 120 (if free torotate on the shaft) to rotate as well about the axis 210. In someaspects, such rotation of the frame 120 may be desirable, for example,for automatic cleaning of the PV cells 110 by periodically rotating thesolar panel 105 through the cleaning solution 135. In some aspects, therotational speed of the spherical frame 120 may be based at leastpartially on a temperature gradient between the heated material (forexample, magnetized fluid within the upper hemisphere 215) and thecooled material (for example, magnetized fluid within the lowerhemisphere 220).

While this disclosure contains many specifics, these should not beconstrued as limitations on the scope of the disclosure or of what maybe claimed, but rather as descriptions of features specific toparticular implementations of the disclosure. Certain features that aredescribed in this disclosure in the context of separate implementationscan also be provided in combination in a single implementation.Conversely, various features that are described in the context of asingle implementation can also be provided in multiple implementationsseparately or in any suitable sub-combination. Moreover, althoughfeatures may be described above as acting in certain combinations andeven initially claimed as such, one or more features from a claimedcombination can in some cases be excised from the combination, and theclaimed combination may be directed to a sub-combination or variation ofa sub-combination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular implementations of the present disclosure have beendescribed. Other implementation s are within the scope of the followingclaims. For example, the actions recited in the claims can be performedin a different order and still achieve desirable results.

What is claimed is:
 1. A solar power system, comprising: a plurality ofsolar power cells mounted on an outer surface of a spherical frame, thespherical frame comprising an inner surface that defines an interiorvolume; a heat sink that comprises a hollow housing mounted and enclosedwithin the interior volume of the spherical frame, the hollow housingfluidly isolating an inner volume of the hollow housing from a housingvolume defined between the hollow housing and the inner surface of thespherical frame, the housing volume comprising an annulus cross-section;and a phase change material positioned in, and fluidly sealed within,the inner volume of the hollow housing of the heat sink such that thephase change material is fluidly isolated from the housing volume of theinterior volume of the spherical frame, the phase change materialthermally coupled to the inner surface of the spherical frame throughthe hollow housing and the housing volume to receive heat from the outersurface of the spherical frame.
 2. The solar power system of claim 1,wherein the plurality of solar power cells comprise a plurality ofphotovoltaic (PV) cells.
 3. The solar power system of claim 1, whereinthe phase change material comprises at least one paraffin wax.
 4. Thesolar power system of claim 1, further comprising at least one permanentmagnet mounted within the hollow housing.
 5. The solar power system ofclaim 4, wherein the at least one permanent magnet is mounted within thehollow housing on a shaft that extends through a diameter of thespherical frame and the heat sink.
 6. The solar power system of claim 4,wherein the at least one permanent magnet comprises a hollow magnet thatencloses the phase change material.
 7. The solar power system of claim6, further comprising a magnetized heat transfer fluid disposed andflowable within the housing volume between the hollow magnet and theinner surface of the spherical frame based on at least one of (i) anamount of heat transferred from the outer surface of the spherical frameinto the magnetized heat transfer fluid, or (ii) a magnetic fieldgenerated by the hollow magnet.
 8. The solar power system of claim 7,further comprising a plurality of baffles mounted within the interiorvolume of the spherical frame between the hollow housing and the innersurface of the spherical frame, the plurality of baffles forming atleast one flowpath for the magnetized heat transfer fluid within theinterior volume that is oriented along a circumference of the interiorsurface of the spherical frame.
 9. The solar power system of claim 1,further comprising at least one permanent ring magnet circumferentiallymounted adjacent an outer surface of the spherical frame.
 10. The solarpower system of claim 9, further comprising a magnetized heat transferfluid disposed and flowable within the housing volume between the heatsink and the inner surface of the spherical frame based on at least oneof (i) an amount of heat transferred from the outer surface of thespherical frame into the magnetized heat transfer fluid, or (ii) amagnetic field generated by the permanent ring magnet.
 11. The solarpower system of claim 1, wherein the hollow housing is spherical, andthe solar power system further comprises at least one permanent magnetmounted within the interior volume on a shaft that extends through adiameter of the spherical frame and the hollow housing, the at least onepermanent magnet comprising a hollow magnet that encloses the phasechange material, and the at least one permanent magnet is configured torotate on the shaft.
 12. The solar power system of claim 5, wherein theat least one permanent magnet comprises a hollow magnet that enclosesthe phase change material.
 13. The solar power system of claim 12,further comprising a magnetized heat transfer fluid disposed andflowable within the housing volume between the hollow housing and theinner surface of the spherical frame based on at least one of (i) anamount of heat transferred from the outer surface of the spherical frameinto the magnetized heat transfer fluid, or (ii) a magnetic fieldgenerated by the hollow magnet.
 14. The solar power system of claim 1,wherein the hollow housing is spherical.
 15. The solar power system ofclaim 14, further comprising at least one permanent magnet mountedwithin the housing volume on a shaft that extends through a diameter ofthe spherical frame and the hollow housing, the at least one permanentmagnet comprising a hollow magnet that encloses the phase changematerial.
 16. The solar power system of claim 15, wherein the at leastone permanent magnet is configured to rotate on the shaft.
 17. The solarpower system of claim 14, further comprising at least one permanent ringmagnet circumferentially mounted adjacent an outer surface of thespherical frame.
 18. The solar power system of claim 17, furthercomprising a magnetized heat transfer fluid disposed and flowable withinthe housing volume between the heat sink and the inner surface of thespherical frame based on at least one of (i) an amount of heattransferred from the outer surface of the spherical frame into themagnetized heat transfer fluid, or (ii) a magnetic field generated bythe permanent ring magnet.
 19. The solar power system of claim 18,wherein the plurality of solar power cells comprise a plurality ofphotovoltaic (PV) cells.
 20. The solar power system of claim 19, whereinthe phase change material comprises at least one paraffin wax.